Unmasking antigens for immunohistochemistry

Preservation of tissue by fixation in a formalin solution, followed by dehydration and paraffin-wax embedding remains the predominant method of preparation for microscopic analysis of morphology. Whilst this may be optimal for morphological assessment, this technique has major disadvantages for subsequent immunohistochemical study as a result of the structural alteration of antigens that occurs during the processing procedure. However, the introduction of a range of antigen unmasking procedures has revolutionised immunohistochemistry, establishing the technique as a powerful tool in diagnostic pathology. Here, the development of enzymatic, non-enzymatic and heat-based antigen retrieval techniques is reviewed, and the methods in use currently are appraised.